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I,n1 E C 0 R 7-Eleven Store#19976 Quarterly Groundwater Monitoring and Remediation Progress Report(2Q2005) August 9, 2005 Page 5 1 On April 9, 2004, SECOR submitted a request with the SJCEHD to reduce sampling of MW-4 and MW-4A from quarterly to annually Approval was received in a letter from the vlp� SJCEHD dated July 28, 2004 ` On June 2, 2004 a 22-hour SVE event was conducted on the horizontal tank pit wells Based on soil vapor samples collected during the test it is estimated that approximately 0 10 pound of TPHg was removed in sod vapor during the 22-hour test No recordable ', amount of benzene or MtBE was removed during the test la ° On November 23, 2004, an additional SVE test was conducted on monitoring well MW-2 Based on the soil vapor samples collected during the five hour test, approximately 1 79 lbs k ' " of TPHg was removed No recordable amounts of benzene or MtBE were removed during ' the test r On March 15, 2005, SECOR submitted a Work Plan for OZ Sparge Well Installation to the SJCEHD This work plan details the proposed installation of three oxygen injection wells to improve the remediation at the site 1 31,E In a letter dated May 3, 2005, the SJCEHD stated that the work plan would have to be approved by the California Regional Water Quality Control Board (CRWQCB) before the SJCEHD could comment on it The letter also directed 7-Eleven, Inc to sample MW-4 semi-annually and MW-4A quarterly On June 27, 2005, SECOR submitted a work plan for additional site assessment to the SJCEHD The work plan proposed the addition of MW-8 to the west of MW-2 The workr plan was approved in a letter dated July 11, 2005 >L4 MONITORING AND SAMPLING PROCEDURES r The depth to water was measured to within 0 01 feet bgs in monitoring wells MW-1 through ' MW-7, MW-1A, MW-4A, and MW-5A from the top of casing (TOC) using a water level indicator Dissolved oxygen concentrations were measured in wells MW-1, MW-1A, MW-2, MW-3, MW-5, MW-5A, MW-6, and MW-7 using a YSI Model 550A dissolved oxygen meter equipped with a down hole sensor r' Well purging and sampling equipment was thoroughly cleaned prior to purging and sampling each well The sampling procedure for each well included measuring the water ' level and checking for the presence of liquid-phase hydrocarbons (LPH), using either an electronic indicator and a clear Teflon' bailer or an oil-water interface probe Wells not containing LPH were purged of approximately three casing volumes of water (or to dryness) using a submersible pump or bailer The equipment and purging methods used for the current sampling event were noted on the field data sheets shown in Attachment A During purging, temperature, pH, and electrical conductivity were monitored After purging, water levels were allowed to recover to 80% of the original levels prior to collection of the water sample Groundwater samples were collected using a disposable Teflon® bailer, placed into appropriate EPA-approved containers, labeled, logged onto chain-of-custody w documents, and transported on ice to a California state-certified laboratory Copies of the r4 . field notes are presented in Attachment A , y � r u� 19976 05-2Q Report doc SECOR Intematronal Incorporated Ffi ' 'I